The British Parliament passed a law granting independence in July 1947. The law gave people only one month to decide which country they wanted to live in and to move there. As millions of people began to move, more violence broke out.
Calderas form when an enormous magma chamber under, what was probably a pretty ginormous volcano, empties and collapses, causing the land above it to collapse as well. An explosive caldera-forming eruption has never been witnessed first hand, but we know that they should pretty fearsome spectacles. Much smaller calderas atop effusive volcanoes (hawaiian style) have been observed. So, formation: maars form when a vent intersects groundwater and blasts out the overlying material.
Amazingly, the caldera collapse didn't occur at the eruption vent, but 10 km away at Katmai, a stratovolcano! Apparently magma drained away from Katmai's magma reservoir to Novarupta's erupting vent. Yellowstone National Park consists of three enormous calderas that erupted about 2, 1.2, and 0.6 million years ago. The most recent caldera is 45 km across and 75 km long! Caldera-forming eruptions are the largest eruptions on Earth. For example, the Fish Canyon eruption in southwestern Colorado about 28 million years ago erupted more than 5,000 cubic kilometers of magma from the La Garita caldera.